1. Field of the Invention
The present invention relates to a nonreciprocal circuit device, and more particularly, to a nonreciprocal circuit device such as an isolator or a circulator used in a microwave band. The present invention further relates to a communication apparatus using this nonreciprocal circuit device.
2. Description of the Related Art
Generally, a lumped-constant type isolator used for mobile communication equipment such as portable telephones performs the function of passing signals only in the transmission direction, and of blocking the transmission thereof in the opposite direction. In recent years, mobile communication equipment is in an increasing demand for cost reduction, as well as that for the reduction in size and weight, because of its use. Correspondingly, the isolator is also required to be reduced in size, weight, and cost.
As such a lumped-constant type isolator, an isolator is shown in FIG. 9. In this lumped-constant type isolator 11, a resin terminal case 13 is disposed on a metallic lower case portion 12, which has left and right side walls 12a and a bottom wall 12b, and a center electrode assembly 14 is accommodated in this terminal case 13. A metallic upper case portion 15 is placed on the metallic lower case portion 12. A permanent magnet 16 is stuck on the inner surface of the metallic upper case portion 15, and it applies a DC magnetic field to the center electrode assembly 14.
In the center electrode assembly 14, three center electrodes 21 to 23 are arranged on the top surface of the microwave ferrite 20 so as to intersect each other at an angle of substantially 120 degrees, in an electrical insulation state. In these center electrodes 21 to 23, port portions P1 to P3 on one end sides thereof are led out horizontally, and a shield portion on the other end side which is common to the center electrodes 21 to 23, is abutted against the bottom surface of the ferrite 20. The common shield portion substantially covers the entire bottom surface of the ferrite 20, and is connected to the bottom wall 12b of the lower case portion 12, through a window portion 13a of the terminal case 13.
The port portions P1 to P3 of the center electrodes 21 to 23 are connected to the hot-side capacitor electrodes of the matching capacitors C1 to C3, respectively. On end of a terminating resistor R is connected to the hot-side capacitor electrode of the matching capacitor 3. The center electrode assembly 14, capacitors C1 to C3, etc. are accommodated in the terminal case 13.
Meanwhile, the terminal case 13 of the isolator 11 is provided with guide portions (the window portion 13a and the recess 13b shown in FIG. 10 correspond to these), in order to position the center electrode assembly 14, the capacitors C1 to C3, etc. as built-in components, when accommodating them. However, in order to assemble the isolator 11 utilizing an automatic assembling machine, it is necessary to ensure a clearance not smaller than 0.1 mm between the center electrode assembly 14 and the window portion 13a, or between the capacitor C3 and the recess 13b, by increasing the dimensions of the window portion 13a and the recess 13b. This raises a problem, however, that the position of each of the center electrode assembly 14 and the capacitor C3 varies by the amount of the clearance thereof, so that the electrical characteristics of the isolator 11 vary.
Accordingly, it is an object of the present invention to provide a nonreciprocal circuit device which can be assembled by an automatic assembling machine, and in which the built-in components thereof can be disposed with a high positioning accuracy, and to provide a communication apparatus using this nonreciprocal circuit device.
In order to achieve the above-described object, the present invention provides a nonreciprocal circuit in which guide portions for positioning the nonreciprocal circuit components with respect to the resin case are provided, and the guide portions have tapered side wall surfaces. Herein, it is preferable that the taper angle of each of the side wall surfaces be not more than 60 degrees. Particularly, by setting the taper angle of each of the side wall surfaces to be not more than 10 degrees, the miniaturization of the nonreciprocal circuit device can be achieved. Here, the nonreciprocal circuit components include, for example, a permanent magnet, a center electrode assembly, matching capacitors, a circuit board comprising a plurality of matching capacitors, and a terminator.
By this construction, since the guide portions are provided with tapered side wall surfaces, it is possible to widen the opening on the component-insertion side of each of the guide portions, and to facilitate the work of assembling nonreciprocal circuit components into the resin case by utilizing the automatic assembling machine. The nonreciprocal circuit components inserted into the guide portions are disposed at predetermined positions with a high positioning accuracy, while being subjected to the correction of positions thereof by the tapered side wall surfaces. Furthermore, by providing notches for center electrodes on the guide portion in which the center electrode assembly is provided, the displacement of the center electrode assembly due to a rotation can also be avoided.
Moreover, the communication apparatus in accordance with the present invention provides superior frequency characteristics by comprising a nonreciprocal circuit device having the above-described features.
The above and other objects, features, and advantages of the present invention will be clear from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings.